The 21-year-old from Glengormley in Northern Ireland had been holidaying on the Mediterranean party island.

The cause of Mr Drennan's death is not yet known.

A former pupil of Glengormley High School, Mr Drennan had worked for the Glasgow-based firm SGL Security, which employs door supervisors.

A British Foreign Office spokesman said: "We can confirm the death of a British citizen in Ibiza on 19 July.

"We have been liaising closely with the Spanish authorities, and are providing support to the family at this difficult time."

Last night, tributes to the popular Northern Ireland supporter were pouring in on social media.

Alan's grieving brother Lee shared his pain and sadness in a heartfelt message on Facebook.

"Nothing is promised to no one, appreciate everything in life because you never know when it can be taken from you.

"I've learnt this the hard way as I've lost a massive part of my life, my wee bro," he wrote.

"After 21 years of listening to his voice every day and always having him to go to if I ever needed anything or vice versa, to be told I'll never have that again is the hardest thing I've ever been through.

"I appreciate everyone's thoughts and prayers for me and my family, also their respect for him. He was one of a kind and it's nice to see so many think so highly of him. Thank you.

"I love you so much Alan. Always."

Lee also placed a poem on a Facebook page dedicated to his younger brother's memory.

"Beloved brother,

Our hearts still ache in sadness

and secret tears still flow

What it meant to lose you

No one will ever know."

There were more than 200 messages of condolence below Lee Drennan's tribute to his brother.

His friend Lee McWhirter wrote: "Thinking of you all mate, can't even start to imagine what you and your family are going through. I'm sure you have heard it hundreds of times today but everyone is here for you."

Another friend, Helen Simpson, said: "Lee I am so sorry to hear. Everyone is here to help you through this. Thoughts are with you and your family. Love you loads."

Assembly member Paula Bradley, whose son had attended Glengormley High with Mr Drennan, said: "This is very sad news. Losing someone like this just doesn't bear thinking about. My thoughts are with his family at this dreadful time."

Newtownabbey councillor Noreen McClelland said: "My thoughts and prayers are with the young man's family. I don't know how any family could cope with such a tragedy. God love them".

Mr Drennan is the fifth Briton to have died on the party island of Ibiza in the last two months.

Scot Robert Gillespie (26) died on a stag night after falling from a fifth floor balcony, while hairdresser Cara Keirl (28) from Bristol died in mysterious circumstances.

Holiday worker Zander Moynes (20) from Berkshire died after taking over-the-counter medicines following a drinking bout.

And Andrew Watson (32) from Newcastle died from a drug overdose while on a stag party break.